This invention relates to a process and to an installation for the purification of effluent or liquid-based waste. It relates more particularly to the purification of effluent with the aid of pure oxygen or enriched air.
In known purification installations, effluent is contained in a tank through the bottom of which oxygen or oxygen-enriched air is injected, the tank being covered so as to permit recovery and recycling of the gaseous phase which accumulates above the surface of the effluent. These installations have the disadvantage that they result in an accumulation of nitrogen (supplied by the enriched air) and of carbon dioxide (resulting from the respiration of microorganisms present in the tank) in the gaseous phase which is recycled; this disadvantage results either in a diminution in the efficiency of purification or in the necessity of providing installations for monitoring the component concentration in the recycled gas, the result therefore being an increase in the cost price of the installation.
Furthermore, in known installations, it is necessary to manipulate large volumes of sludge which makes necessary the presence of large-volume decanting or settling equipment and the presence of recycling instruments which consume a large quantity of energy.